The present invention relates to a process for controlling the driving behavior of an automotive vehicle.
A process of the afore-mentioned type is generally disclosed, for example, in EP 04 441 09 B1. The automotive vehicle with which the conventional process is employed includes, in addition to tire sensors for detecting the forces and moments applied to the tires, a sensor for determining the acceleration in the center of gravity, wheel sensors for detecting the circumferential speed of the individual wheels and a height sensor for determining the condition of the wheel suspension. The use of a sensor for determining the acceleration of the center of gravity requires that the center of gravity of the automotive vehicle is known. However, an automotive vehicle is always exposed to different strain and loading so that the center of gravity, on the one hand, varies due to the inherent movements of the vehicle such as diving or waving motions and, on the other hand, due to different loads. Consequently, a calculation of the vehicle dynamics based on a static center of gravity of the automotive vehicle will not provide accurate values.
U.S. Pat. No. 5,136,513 discloses a method of calculating the vehicle mass and the vehicle center of gravity. The method uses a number of sensors such as a travel sensor or acceleration sensor to determine a location shift, at least one load sensor on the vehicle suspension to determine the vehicle mass as well as a rotation sensor to measure the mass shift during cornering.
It is the object of the present invention to provide a process of the afore-mentioned type permitting a more reliable determination of the vehicle dynamics and requiring only negligible additional sensing efforts.
The principle underlying the invention resides in determining the actual center of gravity of the automotive vehicle from the signals generated by the tire sensor, and in detecting at least the vehicle mass. This process provides actual reference values variable in relation to time, describing the actual driving condition of the automotive vehicle more accurately.
The control quality of a process of this type will be further improved if the automotive vehicle is not statically determined as a pointed mass but rather as a body of finite expansion. Integrated into such a mass distribution model are known masses provided on the automotive vehicle, such as engine, gear box, body and the like spatially distributed items. For example, the vehicle can be described to be a static body suspended from four springs.
To determine the actual mass distribution, additional variable mass can be added to the basic distribution of the mass through the tire sensor signals, with the model, for simplifying purposes, being able to provide additional mass on typical points of load only. Typical points of load are, for example, vehicle seats, luggage compartment and, optionally, the vehicle roof.
The calculation will be particularly simple if the additional masses are defined as mass points located at the centers of gravity of the typical loading sites. These are, for example, the mass center of gravity of an average driver""s body, the center of the bottom of the luggage compartment or the like.
Assuming a static body of a predetermined mass distribution will better mirror real conditions at least in respect of a roof rack load, as in roof loadings, depending on the height of the load, the center of gravity of the vehicle is more or less shifted upwardly, with the aerodynamic drag of the automotive vehicle increasing.
As in view of the tire sensing system the load on the individual wheels is known and, in addition, the center of gravity of the mass is determined, the behavior of the vehicle, under predetermined conditions, can be easily reproduced. It is possible, for example, to compute the lateral guiding force that can be generated by a predetermined wheel when driving through a special curve.
However, it is also possible to determinexe2x80x94with the aid of the mass distribution modelxe2x80x94the momentary driving condition, with no excessively precise computation of the nominal value being required so that also a linear one-track model or the like can by all means be used.